It's not like that's even a relevant argument anyway. SciFi isn't a look, it's a theme, and it's the one closest to Fantasy to the point that there's barely any difference between them and a lot more overlap than many seem to realise. WarCraft is hardly the first to combine them, either, that's been commonplace since at least the early 20th century, if not before. Just look at Jules Verne and the like. Fantastical adventures with what would at the time have been cutting-edge scientific discoveries.
Overlapping the two is about as old as the genre.